The present invention relates to coupling mechanisms for a power tool and, more particularly, to a coupling mechanism used to couple any one of a plurality of power tool heads to a common power tool body.
Coupling mechanisms for power tools are known, for example as disclosed in EP-A-899,063. In this arrangement each head for coupling with the common power tool body has a cylindrical member formed with an annular channel extending all the way around the circumference. The body of the power tool has a U-shaped spring, the arms of which can be splayed apart to form a snap-fit coupling around the annular channel.
In use of the power tool, various problems have been found with such a coupling mechanism. One of the main problems occurs due to the fact that the annular channel extends completely around the circumference of the cylindrical member. A wide area of contact between the spring and the channel can cause the spring to become deformed over time. This deformation is a result of a force being applied to the power tool in use, whereby the force causes a strain to be applied to the coupling mechanism. In extreme circumstances, the spring can become permanently splayed, thereby not effectively coupling the head to the body of the tool.
It is an object of the present invention to alleviate the above shortcomings by provision of a coupling which extends part-circumferentially around the circumference of the cylindrical member, thereby having a relatively limited effect on the spring. Accordingly, the present invention provides a coupling mechanism formed on one portion of a power tool for coupling with a complimentary other portion of the power tool. The mechanism includes a generally cylindrical projection having a side wall with a radial recess formed therein. The radial recess extends part-circumferentially along the side wall and further includes a projection formed on the side wall extending both in a direction parallel to the axis of the cylindrical projection and in a direction radially outward from the side wall. The further projection aids in coupling with the other portion of the power tool and allows for a solid coupling between the portions.
Preferably the further projection includes a chamfer. This enables an efficient snap-fit coupling with the other portion of the tool.
According to a preferred embodiment, the chamfer extends diagonally with respect to both the direction parallel to the axis of the cylindrical projection and to the direction radially outward from the side wall. Such an arrangement allows for a snap-fit coupling between the two portions of the power tool, thereby preventing unaided separation if an attempt is made to pull them apart.
The further projection extends part-circumferentially along the side wall, thereby allowing for accurate alignment with co-operable members on the other portion of the tool. In addition, the further projection may overlap with the radial recess.
Also, the further projection may overly and have the same circumferential extent as the radial recess.
In one embodiment a channel is formed in the side wall and extends parallel to the axis of the cylindrical portion, thereby allowing for further engagement with the other portion of the tool and serves to obviate any relative rotation due to torque being applied to the tool during use. Therefore, the channel may be arranged for engagement with the other portion of the power tool.
Advantageously the side wall of the cylindrical projection has an upper surface formed as a chamfer.
The cylindrical projection may include a plurality of radial projections extending radially outwardly from the side wall. Also four such radial projections may be equi-spaced circumferentially around the side wall.
A preferred embodiment to the present invention will now be described, by way of example only, with reference to the accompanying illustrative drawings in which: